Tips for outreach in Vietnam / Thailand?

Hello,

I work at an agency placing links for a variety of gambling clients. One of them has made it a goal to place some links on Thai and Vietnamese websites.
We did manual outreach to a few thousand sites in these areas but the response rate was minimal. I wonder if we’re not approaching this matter in the right way (we had far better response rates from English-speaking and European territories).

Can anyone share some tips on how we could find link opportunities on Vietnamese and Taiwanese sites?

Thanks a lot in advance
SEMrush