Education visa is a good option for staying long-term in Thailand. You just need to enrol into a course (usually 60 to 180 hour Thai language or English language course) and that will give you 15 months visa that can be extended for up to 5 years. Total cost for 15 months is around 1000 USD and you don't have to leave the country every couple of months. Just Google "thailand education visa". It's also a good way to learn something while staying in Thailand.
No age limit. Most courses are run by small private schools that are flexible with how and when you actually study. Education visa can be arranged before coming to Thailand, or for 500 USD you can change your tourist visa to EDU visa while in Thailand.
