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.