Hi appreciate to recommend some jacket/sweater/hoodie/etc brand as i dont have a decent one. Just bought 1 from North Face , imma still looking a few more as alternate.

I just wear my Uniqlo jacket and shorts. Japan like Cameron highland weather

how about night time ? will it be super cooling and windy?

18-20 deg C for short duration exposure is still bearable but if 18-20 Deg C > 1h, it is freaking freezing cold.

Advisable to wear a Long Johns internally before putting up any other long pant or long sleeve shirt / jacket.

If day time 18-20 Deg, expect night time to fall by 6 to 7 deg C = 11~13 deg C range.

If your hotel got heater, it should not be an issue. After this, you will probably understand why 4 seasons climate country's ppl love the heater.

A simple and cheap zara wool jacket will keep you plenty warm. It helped me in -4 degree German cold.

In fact any ordinary jacket or hoodie is enough for the weather you’re talkin about, it’s nothing m8.

In Doha’s winter it gets hella windy at 12 degrees, and a thick hoodie or bomber jacket keeps me comfortable.

20 degrees under the sun - hoodie cukup

20 degrees, rain - rain jacket

bottoms - jeans should be enough

no need long johns... those are for real winter, snow, single digit degree temperature