What is the best way to obtain a retirement visa in Thailand if I can't get one from the Thai embassy in Hong Kong?

there is no down side to getting a single entry tourist visa before you wing your way here. I'm sure it's available from the thai consulate there. That will give you 60 days when you stamp in and provide you with plenty of time to get your shit together to apply for the in country Non-O visa with enough time left on your entry stamp (based on what office you use).

That's what I'd do anyway. BUT as people pointed out, either a visa exempt entry OR a tourist visa entry will work for the conversion.

Visa Exempt Entry is 30 days, with 14 days quarantine and 15 days left needed it is a very tight time frame. You have to apply for an Extension of Stay based on tourism first to gain more time. Application cost 1.900 thb or apply before travel for the tourist visa which give you 60 days at entree.

EDIT: Quarantine days depends on picture shown below.

My advice would be to enter on a visa exempt, and then purchase a 90 day in-country Non-O visa based on retirement. When there's 45 days or less remaining on the existing stamp, then apply for a one year extension of stay based on retirement.

For the 90 day in-country Non-O visa, you will need AT LEAST 15 days remaining on your existing admitted to stamp.

For the Non-O visa acquired inside Thailand, you will need the following:

1. Your passport and a copy of:

a. The data “picture” page.

b. The most recent visa (if applicable).

c. The most recent entry stamp or extension of stay (if applicable).

d. The departure card (“TM 6”) stapled in the passport.

2. If entered on a tourist visa, a TM 86 visa change request form, and if entered on a visa on arrival, visa exempt, or bilateral agreement, a TM 87 visa change request form.

3. Proof of a TM 30 filed at the immigration office.

4. A letter from a Thai bank showing that 800,000 THB was transferred into the bank account from overseas, or pension from overseas of no less then 65,000 THB a month, or a combination of both income and pension, totaling 800,000 THB.

5. A hand drawn map to the house where the applicant lives.

6. 2x passport sized (4cm by 6cm) photos.

7. A processing fee of 2,000 THB.

For the one year extension of stay based on retirement, you will need the following:

1. Your passport and a copy of:

a. The data “picture” page.

b. The most recent visa (if applicable).

c. The most recent entry stamp or extension of stay (if applicable).

d. The departure card (“TM 6”) stapled in the passport.

e. A TM 30 filed at the local immigration office

2. To meet the financial requirements of either:

- 800,000 THB in a Thai bank account seasoned for 2 months along with a letter from the bank. If renewing the one year extension of stay, the 800,000 THB must be seasoned for two months before applying and three months after the last extension of stay was granted, and for the money not to have been lower then 400,000 THB throughout the calendar year, Or;

- 65,000 THB a month in income to a Thai bank transferred from overseas, Or;

- A letter from the embassy stating the applicant receives 65,000 THB a month in income from overseas.

3. A hand drawn map to the applicant’s residence. Some immigration offices may want this map on a special paper.

4. 2x passport sized (4cm by 6cm) photos.

5. A processing fee of 1,900 THB.

There is an under consideration period for this extension of stay. This may include an at-home visit by the immigration office to confirm the applicant is residing at the address, and if using the banked money method, to confirm the money is still in the bank account. The immigration office will give a list of the documents required to bring to the immigration office when the under consideration stamp is closed out.