I suggest you avail of this package https://www.bangkokhospital.com/en/bangkok-bone-brain/package/carotid-doppler-ultrasound
Note that you have to buy online to get that price
If you prefer other hospital then here (bit a bit more expensive) https://mbrace.bnhhospital.com/en/product/carotid-doppler-ultrasound/
It will include doctor visit to explain findings then you can take it from there if significant blockage is found.
The fact that your dizziness is only upon standing up is more consistent with orthostatic hypotension than anything else. But, as you have had prior finding of mild carotid plaques, good idea anyway to recheck. (Orhtostatic hypotension is common in older people especially -- but not only -- if on blood pressure mediction. Best managed by getting up slowly and, sometimes, by adjusting BP medication dose or schedule).
People with carotid plaques often also have some plaque build up in the coronary arteries. A Coronary Calcium Scan may be good idea if you have not had one, or other test (like angiogram etc) in the past few years. Same hospitals offer package for this
https://www.bangkokhospital.com/en/bangkok-heart/package/ct-coronary-calcium-score
https://mbrace.bnhhospital.com/en/product/ct-calcium-score-screening/?srsltid=AfmBOorsy7LsOjNTm5QpkG-9DNCmb34ZU51aTHiXWvCoQo0V32oTs96Z
While BNH is more expensive for both tests they also have a package that combines Carotid Doppler, CAC and low dose lung CT (screening for lung cancer) at a competitive price (15k for all 3), relevant only if you need that last one. Annual low dose lung CT is indicated only if you are "aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years" https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/lung-cancer-screening