Thailand has a very efficient postal service and within the country it's also very cheap. Bangkok's GPO on Charoen Krung (New) Road is open from 8 am to 8 pm Monday to Friday and from 9 am to 1 pm weekends and holidays. There is a telephone and telegram service 24 hours a day. Outside of Bangkok, most post offices close at 4.30 pm on weekdays and only the larger ones are open a half day on Saturday.
The poste restante service is also very reliable, though during high tourist months (December and August) you may have to wait inline at the Bangkok GPO. There is a fee of 1 Baht for every piece of mail collected. As with many Asian countries, confusion at poste restante is most likely to arise over given names and surnames. Ask people who are writing to you to print your surname clearly and to underline it. If you're certain a letter should be waiting for you and it cannot be found, it's always wise to check it hasn't been filed under your given name. You can take poste restante at almost any post office in Thailand now.
The American Express office, Suite 414, Siam Center, Rama IV Road, will also take mail on behalf of AMEX cardholders. The hours are from 8.30 am to 12 midday and 1 pm to 4 pm, Monday to Friday.
Parcels shipped by surface post vary from 174 Baht for 1 kilogramme up to 800 Baht for weights of up to 15 kilogrammes.
The telephone system in Thailand is quite efficient and from Bangkok you can usually direct dial most major centres with little difficulty. The opposite may not always apply, and in smaller centres it's often best to go to the local telephone office (usually located at the central post office) and make calls from there. You can make international long-distance calls from government telephone offices or from large hotels; it is always cheaper to call abroad from a telephone office. There are also private long-distance telephone offices but these are not for international calls, only for calls within Thailand.
There are two kinds of public pay phones in Thailand, 'red' and 'blue'. The red phones are for local city calls and the blue are for long-distance (within Thailand) calls. Local calls from pay phones cost 1 Baht. Although there is three different 1 Baht coins in general circulation, only the middle-sized coin fits the coin slots.
Electric current is 220 volts, 50 cycles.
Thai time is seven hours ahead of GMT (London). Thus 12 noon in Bangkok is 3 pm in Sydney, 1 pm in Perth, 5 am in London, 1 am in New York and 10 pm the previous day in Los Angeles.
Most government offices are open from 8.30 am to 4.30 pm, Monday to Friday, but closed from 12 noon to 1 pm for lunch. Banks are open from 8.30 am to 3.30 pm Monday to Friday, but in Bangkok in particular several banks have special foreign exchange offices which are open longer hours (generally until 8 pm) and every day of the week.
Businesses usually operate between 8.30 am to 5 pm, Monday to Friday and sometimes Saturday morning as well. Larger shops usually open from 10 am to 6.30 or 7 pm but smaller shops may open earlier and close later.
The metric system was officially introduced by a law passed on December 17, 1923. However, old Thai units are still in common use, especially for measurements of land which is often quoted using the traditional Thai system of waa, ngaan and rai. Old-timers in the provinces will occasionally use the traditional Thai system of weights and measures in speech, as will boat-builders, carpenters and other craftsmen when talking about their work. Here are some conversions to use for such occasions:
| Thai system | Metric System |
| 1 square waa | 4 square metres |
| 1 ngaan (100 square waa) | 400 square metres |
| 1 rai (4 ngaan) (1 square sen) | 1600 square metres |
| 1 baht | 15.16 grammes |
| 1 taleung¹ (4 baht) | 60 grammes |
| 1 chang (20 taleung) | 1.2 kilogrammes |
| 1 haap (50 chang) | 60 kilogrammes |
| 1 niu | 2 centimetres |
| 1 kheup (12 niu) | 25 centimetres |
| 1 sawk (2 kheup) | 50 centimetres |
| 1 waa (4 sawk) | 2 metres |
| 1 sen (20 waa) | 40 metres |
| 1 yoht (400 sen) | 16 kilometres |
| 1 kwien | 2,000 litres |
| 1 ban | 1,000 litres (2 ban=1 kwien) |
| 1 sat | 20 litres (50 sat=1 ban) |
| 1 tannan | 1 litre (20 tannan=1 sat) |
| ¹Also tamleung | |