Yaris in Thailand needs help with suspension tuning

[KooKatt]

I use Yaris G-limited in Bangkok. The road condition here is not very good. Hence, I would like to improve the suspension without dropping the car height. I would be grateful if you can give me some suggestion.

So far, all I did is install Ultra Racing rear sway bar. Since it is not a popular tuning here in Thailand, I can only find 16mm sway bar. I know that it might not be as good as 23mm but I think it is better than none at all. Do you think it is worth upgrading to 23mm?

Another thing that I need some more input. I would like to replace OEM shock and spring. Tein and TRD Sportivo package are very popular here but I found the ride is too low. And to be honest, it is rather uncomfortable driving these setup in Thailand. Thus, I am exploring other option. One solution I think is that I will use OEM spring from Yaris S-limited which is a bit lower (10mm) and more firm than mine OEM setup with some improve shock absorber e.g. TRD sportivo or Kayaba New SR Special. Or I could just use my current OEM spring with Kayaba Excel-G.

Any opinion or suggestion are welcome and greatly appreciate.

Thank you