If I arrive in Thailand without a visa and receive a 30 day tourist entry stamp can I be sure that I will be able to extend this for at least another 15 days at the immigration near me or by leaving the country and re-entering by air.
Thank you.
TLDR : Answer Summary
Yes, if you enter Thailand without a visa and receive a 30-day tourist entry stamp, you can extend it by 30 days at an immigration office, provided your passport is eligible for visa-exempt entry. The extension will typically cost around 1,900 baht and you should apply for it when you have about a week left on your original stamp. After the extension, if you wish to stay longer, you will need to leave Thailand and re-enter.