The name tag should be the most commonly used and default name. This does not imply that everything in Thailand must be written in Thai script. For such reason, we already have name:th. (see discussion at https://community.openstreetmap.org/t/name-tags-for-brand-names-like-bigc-tesco-lotus-or-shell/50548 ). For the private name that the big sign is in English, with a very little Thai in some signs, we should follow the "ground truth principle"