In spite of the fact that visa formalities are comparatively strict, Thailand is in principle an open country.

Visitors wishing to stay in the kingdom for more than 15 days must apply for an entry visa from a Thai diplomatic mission in any country. In the event there are no Thai diplomatic missions in their home country, they may apply to a mission in a neighboring country.
A visa must be used within a period of 90 days from the date of issue; unless an extension is obtained, it otherwise becomes void. The tourist visa permits a stay of up to 60 days . It can be extended once by 30 days.

Under Thai immigration law, those who stay illegally are detained for a certain period of time prior to deportation. The stiff fine of 200 Thai Baht per day is imposed on those who overstay their visa. The fine is collected at the airport rather informally. However, without paying, departure is not permitted.

The inclusion of a child or children on a parent's passport can cause problems if the parent wants to travel out of Thailand without the child or children. Thai immigration laws prescribe that a child sharing a parent's passport must leave the country with the parent. The solution is to have separate passports issued for children.