A truck body is chosen once and lived with on every trip. A closed box, a curtain-sided body with a rigid roof and an open flat bed under a tarpaulin all move the same pallets. They behave very differently on a wet afternoon in September.
This article is about one part of that choice: rain. Thailand's rainy season is long and the numbers are published, so you can plan for it instead of reacting to it.
The short answer
- Rain is not a rare event here. Bangkok averages 128 rainy days a year. In September it is 21 days out of 30.
- The season is not the same everywhere. The south peaks in November, not September.
- Match the body to the goods. Anything that is damaged by water or that tempts a thief belongs in a closed body. Steel, timber and bulk can ride open.
- An open body costs time as well as risk. Roping and sheeting a load is skilled, slow work, and the minutes are a cost on every trip.
- Thai law does not settle who bears rain damage. Your booking does. Write the body type into it.
What the bodies do
This section follows the vehicle selection chapter of the textbook.
| Body | What it is good at | What it costs you |
|---|---|---|
| Closed box | Protects from all weather and cuts pilferage, because it is enclosed and can be locked. Suits pallets loaded by forklift through the rear | Side access is limited. Loading from above is not possible |
| Curtain-sided, rigid roof | Side access to the load, and no roping and sheeting. Works for weather protection and for loading from the side | A fabric side is easier to get through than a locked box, so it offers less theft protection |
| Flat bed, open | Any shape, any loading direction, including by crane from above. Fine for goods that rain cannot hurt | Most loads need roping and sheeting, which the textbook calls skilled and time-consuming. No protection if the sheet fails |
| Tilt (fabric over a frame) | Covers the load without a loose sheet | Stripping the frame to load from above or the side is slow, slower than with a curtain-sided body |
| Tipper | Discharges bulk such as sand, gravel, grain or cement by tipping | Only for bulk. May need a cover |
Two points in the textbook matter for rain.
- The box and the curtain-sider both come from the pallet. The pallet and the forklift made enclosed bodies popular for line-haul. If your goods move on pallets, one of these two is usually the answer.
- Valuable loads are not only the obvious ones. A full truck of ordinary consumer goods is a high-value load. The body is part of the security.
For how the body interacts with load height, door type and tail-lift, see choosing a truck size.
What the rain figures say
The Meteorological Department publishes 30-year averages for 1991 to 2020. The table below shows the mean number of rainy days a year at six stations.
| Station | Rainy days a year | Wettest month | Days in that month |
|---|---|---|---|
| Laem Chabang (1992-2020) | 100.6 | September | 16.7 |
| Khon Kaen | 108.5 | September | 18.4 |
| Chiang Mai | 118.5 | August | 20.9 |
| Bangkok Metropolis | 128.3 | September | 21.4 |
| Songkhla | 159.3 | November | 23.1 |
| Hat Yai Airport | 162.6 | November | 21.1 |
Three things follow.
- Bangkok in the wet season is mostly wet. From May to October the monthly counts are 15.0, 16.4, 17.2, 19.1, 21.4 and 17.0 days. That adds to 106.1 of the 128.3 days in the year, or 83% of the year's rainy days in six months. In the six months from November to April it is 22.2 days.
- A sheeted flat bed in September on a Bangkok lane meets rain on about seven days in ten. 21.4 divided by 30 is 71%. Treat this as a guide. A station counts days with rain at one place, and a truck crosses several.
- The south runs on a different calendar. Songkhla and Hat Yai peak in November, with 23.1 and 21.1 rainy days, when the rest of the country is drying out. A lane to the south needs its protection later in the year than a lane to the north-east.
A rainy day is not a day when everything is soaked. It tells you how often the risk is live, and that is what a body choice is about.
What the law says, and does not say
Road Traffic Act, Section 20. The driver must provide protection so that the load does not fall, leak, smell, reflect light or blow off the vehicle, where that could cause nuisance, dirty the road, harm health or endanger people or property. Read in Thai, this is about the road and other people. It does not say the load must arrive dry. A tarpaulin that stops a load blowing off meets the section even if the goods under it are wet. There is more in securing the load.
Civil and Commercial Code, Section 616. A carrier is liable for loss, damage or delay unless it proves the cause was force majeure, the nature of the goods themselves, or the fault of the sender or the consignee. Rain damage will be argued under one of those. This article does not predict how a court would rule on seasonal rain. What you can control is the facts before it gets there.
- Book the body by name. If you asked for a covered body and the truck arrived open, the argument is easy for you. If you booked "a six-wheeler" and the goods were rain-sensitive, expect a longer argument about whose job it was to say so.
- The decision about who pays is in who pays for damaged goods. That article covers the other defences and the time limits.
A rule for choosing
Ask four questions in this order.
- Does water hurt the goods? Paper, cartons, cement bags, electronics, food and textiles do. Steel bar, timber, bricks and aggregates mostly do not. If water hurts, you need a roof you do not have to build with a sheet.
- How are they loaded? Rear loading by forklift suits a box. Side loading suits a curtain-sider. Loading from above by crane needs a flat bed or a tipper.
- How tempting are they? A full load of consumer goods is a theft risk. A lockable box beats a curtain.
- How many drops? A multi-drop route with side access saves handling time at every stop. A box with only a rear door makes the last pallet loaded the first one out.
If water does not hurt and loading is from above, go open. In every other case, go closed or curtain-sided.
The time cost of open
Roping and sheeting is skilled and slow. The textbook gives no minutes, and this article has none to give, so measure your own.
- Time one sheeting job at your dock, from the last pallet in to the truck moving. Then time the same for a curtain-sided body.
- Multiply. An illustration, not a Thai figure: if sheeting adds 20 minutes and a truck is loaded 20 times a month, that is 400 minutes, or 6.7 hours of the truck's month, before anything rains.
- Put the hours in the quote comparison. The open body often looks cheaper per trip. Whether it is cheaper depends on how many hours it adds. For how to set free time and price waiting, see truck waiting time charges.
What to put in the booking
- The body type by name. Closed box, curtain-sided with rigid roof, or flat bed with tarpaulin. Not just the number of wheels.
- The condition of the roof, curtain or sheet. Ask for it to be free of holes and tears. Look inside the empty body in daylight: if you can see light through the roof, water will come through it too.
- The floor. A wet or oily floor soaks the bottom layer of a pallet.
- A rain rule at your dock. Who decides whether loading stops in heavy rain, and who pays if the truck waits. Say it before it rains.
Where the evidence stops
The rain figures are the Meteorological Department's 30-year averages, one station for each place. A station's count does not describe every road near it, and the report does not define a rainy day in the pages read. No Thai study was found that compares goods damage or cost between closed and open bodies, and the Department of Land Transport's licence statistics are split by vehicle category and not by body type, so no count of Thai trucks by body is given. The advantages and drawbacks of each body come from a British textbook and apply as general method. The worked time example is an illustration. Two statutory claims were checked against Thai text: Road Traffic Act Section 20 on Thai Wikisource, and Civil and Commercial Code Section 616 on two hosts that agree word for word. Nothing was found, and nothing is claimed, about a Thai standard for tarpaulins or truck roofs.