If you are getting married in Thailand then you will need a letter of affirmation or freedom to marry letter from your Embassy in Thailand. The following is a brief breakdown of what each Embassy in Thailand would require from you in order to issue the document.
British Letter of Affirmation
The British and American Embassies are the easiest to issue their letter of affirmation. If you are divorced you will need a copy of your divorce decree or a death certificate if your spouse has died. You will need to complete a form and provide the above mentioned documents. The letter will normally be issued the following day. Note that you can apply for a UK Spouse visa once your marriage has been registered in Thailand.
The Swedish Embassy will require you to have a marriage status paper which is issued in your home country by the local tax authority. You will also need 2 affidavits from friends who can certify that they know you and that you are single. You will also need to provide you parents’ names to the Embassy as well as their occupation in Sweden. The letter can take up to 4 weeks to issue.
New Zealand / Australia
You will need to complete the Statutory Declaration to state that you are single. If you are divorced you will need an Order Dissolving the Marriage to be brought with you to the Embassy. You will also need a death certificate if you wife had passed away. Note that if you got divorced elsewhere you will need to have the divorce decree certified at the Embassy of the country where you got divorced. This is common with New Zealand and Australian citizens in Thailand.
If you are a Moroccan you will need to obtain your marital status letter from your home countries Ministry of Foreign Affairs in Morocco. This documents will be needed from your Embassy in Thailand. Note that you will need to arrange an Islamic conversion in Thailand if you are getting married to a non-Muslim. This is done via the Bangkok Islamic Centre in Thailand. Speak to an attorney about the process.
Note that many law firms will arrange the freedom to get married and file your prenuptial agreement for you as well as file for a US spouse visa as a package deal. These are very common in Thailand. The process much like the British tends to be an overnight process. If you however go on a Friday then you will only get your “Freedom to Marry” the Monday.
If you are going to get married in Thailand then ensure that you have all the needed documents. You will need to ensure that you have your divorce decree as the Embassy in Thailand cannot obtain this for you. If you are a widow then a death certificate will also be needed. The Embassy does not issue these and you will have to bring them from home. Note that certain Gulf Embassies will not issue the Freedom to marry letter unless you are getting married to a Muslim.
Always take legal advice in Thailand before getting married as the marriage laws in Thailand may not be the same as in your home country. Advice on marriage as well as property in Thailand needs to be spoken about.