Can I extend my 30-day visa exemption in Thailand and what is the maximum extension time?

You could enter with a 30 day exemption visa as all have stated extend that at any immigration office 1900 baht that gives you 60 days and you could then do a quick flight to Cambodia or Vietnam (around £50 return) and get another 30 days on arrival and extend that for another 30 days giving you a total of 120 days 👍

You will get 30 days exemption on arrival and you can apply for one 30 days extention of stay.

If you travel without a visa you will receive 30 days when you arrive, and you can apply one time for a 30 day extension from an immigration office while you are here. The day you arrive is counted as day 1.

If you want more time, you should apply for a tourist e-visa through the online system before you come. You don't have to send your passport in anymore, and the London embassy generally issues visas within 3-4 business days.

With a tourist visa you will receive 60 days when you arrive and you can apply one time for a 30 day extension.

You will need to check with your airline what their document policy is for allowing you to board. Some airlines will not let you board with no visa unless you can show travel out of Thailand within 30 days, and some airlines will not let you board your flight with a tourist visa if you cannot show travel out of Thailand within 60 days.