You might check the Amaryllis Forum & look for the posts by someone from Thailand (sorry, forgot his screen name), & email him for some tips.

I would look around the neighborhood & see when people plant & so forth, & maybe ask the neighbors as well.
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Annuals complete their lives within one cycle;
they germinate, grow, flower, fruit, seed, & die.
That will happen no matter where you grow them.

The only difference might be that the seeds would germinate more quickly.

For instance, here in Texas, seeds that ripen & fall to the ground in summer or autumn will lie dormant all winter & sprout in the spring.

If there is no dormant season, they might sprout almost at once.

Perennials survive year after year, each plant going through the cycle over & over again.
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I my own self have always wanted a field of Himalayan Blue Poppies.

can't grow them.

can't grow Alpine plants or Douglas Firs, & can't get tulips to last for more than one season.

There's a quote from a long-gone famous landscape architect whose name I forget:

"Consult the genius of the place."

He meant, grow what'll grow.

Don't try to turn Thailand into Alaska;
Thailand has its own joyous, beautiful, breathtaking character.
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I think the one thing that has helped me the absolute most has been getting knowledge/wisdom/advice from gardeners who have experience in my own area.

If you can find a local gardening club, or if there's something like an Agricultural Extension Service there, absorb all the knowledge you can from them; they're solid gold!

Have fun, & enjoy your garden!

Suggest you check out the Australian forum - particularly for people living in, say, Cairns, QLD or Darwin NT.

Think in terms of equivalents rather than 'same as' when looking at the various garden roles played by temperate zone plants.

Also think in terms of garden safety from local creatures that might be attracted which you wouldn't want to encourage!

You might also want to look at plants such as orchids, Plumeria, bromeliads, ferns and ferny relations/cycads as foundation plants.

Probably a composting system would be very useful for maintaining soil fertility if you plan to do any cropping. Humus breaks down fast with warmth and water.