Hi @Tak.oyaki and welcome to the forum.
As @Angela-CommunityManager says, I have travelled around the region, House and Pet sitting since 2017, with a break during covid back home in Scotland.
There are/were not a lot of sits in SE Asia compared to some other regions, maximum probably round 100 for the whole area in the good days, but also there are not a lot of sitters. A number of sitters will list a country as their location, but this tends to be where they want to sit/travel to rather than their home base.
Things are picking up a bit recently with restrictions being lifted but it is still a bit of a minefield to get into some countries, and you really need to do your homework checking visa/vaccination/test requirements for each individual country. Singapore, Indonesia (Bali) and Thailand are now open but rules change almost daily.
All of the sits I have done have been for ex-pats – mainly from the USA, Canada, Australia, and Europe. A number have been teachers at international schools or executives/professionals with international companies. With the exception of Singapore, all of my sits have been longer durations, when owners travel home – so normally for around a month at a time. Singapore has been a bit of a mix, as you can travel to Bali, Thailand, Malaysia, Vietnam etc from Singapore in under 2 hours, so owners will go for a long weekend.
Pre covid I based myself in Singapore, and have done a number of sits there, and in total have probably spent about a year in the country. I love it. House sitting has let me see so much more of the Island/country than just the city – I think there are about 110 “towns”/districts in Singapore, each with its own park, shops, food courts etc so I find so much more to do in Singapore than most tourists who just visit the city and waterfront for a couple of days. I also got kind of stuck in Singapore for 3 months during lockdown/circuit breaker in 2020.
Visas: as I said above do your homework. Pre covid it was relatively easy to go from country to country, but each had different rules. Most nationalities can/could enter Singapore with a 90-day visa on arrival, but you need to have proof of onward travel/return tickets. This is the same for Thailand and Indonesia, but visa on arrival is for 30 days with an option to extend a further 30 days. Vietnam is only 14 days visa on arrival but it is /was easy to get a 1 month or 3-month tourist visa online before you travel. Japan and Malaysia are both 90 days I think.
Of the 100 sits I mention above, the majority would be Singapore, Thailand, Vietnam, and South Korea. With occasional sits in Malaysia, Bali, Hongkong, Cambodia, Laos, Myanmar, and Japan. I think I have only ever seen 1 in Taiwan and 1 in the Philippines. It is also possible to travel to South India and Sri Lanka from Singapore/Bangkok/KL - hub airports in the region, and even Perth in Australia is only a short 4 ish hour flight.
As far as working in the region goes, it is not that easy, unless you are sent there by your employer. Teaching in international Schools is one of the main employers. I know that Singapore has reduced the number of foreign visas/work permits in the last 2 years, and you now need to be paid quite a high monthly salary to get a work permit for Singapore, so you can’t just turn up and look for a job. Some countries are VERY strict about foreign workers. In Indonesia for instance, you are not even allowed to volunteer without a work visa, although there are a high number of digital nomads, working online, teaching, blogging, and writing, but not actually “working” in Indonesia. You will be deported.
I hope this helps a bit, and if I think of anything else I will add.
It is a great region to visit, travel to, but not so easy to work in.
Peter.