i don't work there but helped my Scottish friend Alister go through the whole procedure as he was unsure. Did you upload all your documents in preparation for your NO Impediment to Marry ceremony at the embassy? If you didn't they refund the money.
Otherwise if you got this and a notarised copy of your passport then ask the embassy.
"Affirmation for the purpose of marriage under Thai law
You need to make an affirmation of marital status in order to get married in Thailand.
This service is available by booking an appointment to attend the British embassy in Bangkok. It costs £50.
Prior to attending an appointment, you need to submit documents online which are checked by consular staff at the embassy.
See getting married abroad to check what documents you must provide and to make an affirmation application.
Same sex marriages/civil partnerships
Same sex marriage is not recognised in Thailand. Therefore, we cannot process documentation for a same sex marriage, even if the marriage is proposed to take place in a third country.
Certified copy of a British passport
This service is available by post or by booking an appointment to attend the British Embassy Bangkok. It costs £25.
You need to submit a valid and original British passport to obtain this service. We cannot accept copies or scans."