, IF you live on the north side (odd number soi side) of Sukhumvit Rd, as you said "Sukhumvit Soi 21", your address has to be Khlong Toei Nuea, Wattana (Vadhana). Khlong Toei, Khlong Toei is on the south side of Sukhumvit Road.
Check your real address. You might need to update TM30, too.
, Singaporean is the exception from the "visa exempt entries two times per calendar year" limit. They can enter Thailand on visa-exempt entry visa land border more than two times per year. Unless regulations have been changed recently.
This type of question has been asked again and again. Usually, we don't approve, asking to check the embassy requirements first.
Yes, this is what you need to check with the exact Thai embassy or consulate where you are going to apply for your tourist visa.
Because each embassy specifies differently.
For example, these are requirements on "proof of in/out travel" copied from different embassy/country sites. Vary widely. Even on the same eVisa web application system. This is the reason why we say "READ the onward travel requirements on their website for the tourist visa".
Embassy A:
A confirmation of transport tickets to enter and depart from Thailand.
Embassy B:
Reservation of a plane ticket from the country or territories as well as an exit ticket from Thailand whose date must not exceed 90 days from the date of arrival in Thailand, with all flight details, including PNR data (Passenger Name Record – 6-element alphanumeric code): information linked to the reservation and contained in the files created by the airlines for each flight) and/or the electronic ticket number
Embassy C:
Flight itinerary for ROUND TRIP ticket (either in Thai or English). The ticket must show the applicant’s name, departure date and time, and flight details
Embassy D:
Evidence of travel from Thailand (air ticket paid in full).
Embassy E:
One copy of confirmed airline ticket paid in full or ticket reservation confirmation. The confirmed airline ticket paid in full or ticket reservation confirmation must be issued by airline or travel company and must contain the applicant's name, flight number, date of arrival and date of departure