neshi I'm of similar age to you but have very oily skin so my recommendations may not be the best, but based on my experience and reviews I can recommend the following:
acid toners - I use Cosrx BHA Blackhead Power Liquid and Cosrx AHA 7 Whitehead power liquid. Since you have dry skin the AHA is probably more of interest - I use this and like it as its a light weight liquid. The only negative is the smell of this one - smells like fish to me, though apparently not everyone smells it.
Moisturiser - I use retinols and acid most days so I am using heavier creams than I would otherwise. I really like rosette ceramide gel as it contains ceramides etc which help repair the skin barrier after acids. Another popular one for dry skin is Mr Honey and miss Flower cream and also the essence oil. I have the cream and its a waxy cream which smells gorgeous.
Serums - I use lots of ampoules rather than serums as I like to layer a few and these seem to be lighter. For dry skin I would recommend LJH Propolis ampoule. Really brightens and softens my skin.
Sleeping masks - def a good idea for dry skins as they seal in moisture overnight. I like bioessence sleeping beauty mask, laneige water sleeping mask or sulwhasoo revitalising overnight mask. Sleeping masks all do the same job (which is to act as an occlusive layer to keep moisture in) but some will suit your skin better than others.
Re shops - not sure what is available in thailand but if its the same as malaysia there was quite a few - watsons is like boots and you will find brands like secret key, bioessence, and other cheaper brands. Sasas is a bit like sephora they sell lots of cosmetics and higher brands like dr jart, sulwhasoo etc. Also shops like etude house, tony moly, skinfood are all worth a look.
Sorry its a huge post! Any other Qs just ask