I am from Hong Kong and yes you are right that applicant should have no criminal records in Thailand and, I assume, place of origin. Please send the "Documents required for Special Tourist Visa class STV" handed over to me by embassy. It can give you a better idea. Apology for bad quality of photo.
I am fully aware the STV has been put on hold till after Phuket Vegetarian festival. However I will not be surprised that some still can get the visa as my knowing about Thailand is that nothing is for sure. I could be wrong. In contrast of your disappointed situation, we don’t need anything in Hong Kong. Just pop up in the embassy, get a number, your questions will be answered.
You could be right but here it seems embassy gives out STV info paper to both local and foreigners. The foreigners might have already obtained Hong Kong ID card. For the low risk country list I keep trying to get the list. Seems it is not available for public so far. Therefore it does not hurt to check out with embassy.
You might want to check the Thailand embassy again. I went to the Thai embassy in Hong Kong on Oct 6, the staff said we can apply STV and handed out a piece of paper with all the requirements and required document. I did ask if I needed to be a group and the staff said no. Once STV is issued we can take the repatriation flight or commercial flight (non-chartered flight) to go to Thailand. Since I am not applying for STV I didn’t ask further. But if you can get STV you can meet your fiancé. Embassy staffs also said that besides Thai airway which has very limited flight we can take Cathay Pacific CX653 which is available 4-5 times a week. The similar arrangement could be available in your country.