I have just come to Thailand on a multipul entry visa and will apply for retirement visa soon, you need to show an account with 800,000 baht or an income of 65,000 per month, you will also need a police record check on yourself by your home police force and your birth certificate, when you arrive in Thailand you will need to get a Thai Doctor to check you over, then take all the above to Thai immigration for 1 year retirement visa, this can be renewed every 3 months at immigration without leaving the country. Hope this helps