I have just received the 90 day Non O visa as a dependant on my husband's retirement visa. We did it this way as I am not 50 yet and also we do not have to have the extra 800,000 baht in a Thai bank for my visa. We went to Penang in Malaysia as it seems the only consulate that is giving out this type of visa at the moment. We needed to show the usual visa documents (passports, photos, bank statements etc) as well as our English marriage certificate. To apply for the year extension we need to have our marriage certificate legalised in the UK by the FCO and then the marriage certificate must be translated into Thai and then the translation has to be certified at the MFA in Bangkok. After this we have to have the marriage recognized in Pai , Mae Hong Son where we live. If your parents are still in the UK it is worth them getting their marriage certificate certified and possibly notarised if they married in a church before they come to Thailand as it is time consuming and costly to send the certificate to England from Thailand. I hope this helps, it is quite hard to find out information on couples where neither is Thai.