Thailand has an extremely strict anti-narcotics law that provides for severe sentences, including the death penalty, for narcotics traffickers and users. Several hundred foreigners are imprisoned in Thailand on narcotics charges, a number of whom are serving life sentences. In higher-elevation northern Thailand, a jacket or sweater is needed during the cool season. Western-style clothes are the norm in the Bangkok, with shirt and tie necessary for business. Jackets are necessary only for more formal occasions given the heat and humidity.
External appearance matters a great deal to Thais.
Regulations and requirements for international travel may change at short notice. In General, avoid the two weeks before and after Christmas. Thai holidays are based on both the Chinese and Buddhist calendars, some of which vary from year to year. Most local businessmen vacation in April or May. However, Bangkok metropolitan area traffic is legendary for its congestion - vying for being the worst in the world.