Personal opinion. As an Asian person, don’t overthink this. Just have fields for family name and given name to distinguish between the two. Sure, when there’s a text field saying hello “first name last name” it might be flipped but this shouldn’t be a deal breaker or offensive in any capacity. Worst case is you can have a toggle they can click but from a developer standpoint, that might be over engineering for someth…
Well, if the app is designed for the asia pacific region then last name first name should be default to fit the majority of user's expectation, no?
For instance in China, most names are single character family name followed by a two character given name. Some rare family names are two characters and usually they will have a single character given name. Some people have single character family name and single character given name.
Then you get people from different ethnic groups who put the family name at the end. Often these are characterised by a long given name and then an interpunct joining that with the family name, but that's not always done. For instance a popular singer at the moment has the Chinese name 希林娜依·高 where 高 is a fairly normal Chinese surname so it's easy to identify as such. A very popular actress is named 迪丽热巴·迪力木拉提 so it's not always the case you can easily tell which name is which.
Even for those with simple construction, so the characters are FAB (family name, and 2 characters for given name). You'll find that within a family, where you might expect pet names, it's common instead to call each other by AB, except when they're annoyed and use the full name FAB. In a business context, someone with a higher rank might be F先生 (Mr F), F总 (Manager F), F董 (Director F), but close colleagues might call you AA, BB, 小A, 小B etc - but typically they won't get to choose that, they'll be told by the person "you can call me ___" and they might allow different people to use different names or react with their official title if someone uses too informal a name with them.
I've got Chinese friends who exclusively use an English name at work in China. I've got a friend who later moved to the UK, and most people in the UK know her by her Chinese name, but except for a few close school friends, nobody in her working life in China even knew her real name because the company she worked for only used English names (this isn't very common though).
In other countries, many people don't use their first name much. In the UK, I've known quite a few people who've primarily used their middle name, and others (including me) are generally known by others with a name that isn't among any of their given names. Sometimes these are common transformations, e.g. David to Dave, David to Dai (in Wales), but other times people just use initials or nicknames (e.g. I've got a friend who pretty everybody calls Danger, it started as a joke with friends, but now even his parents sometimes use it!)
Anyway, that was a long diversion, but it's always safer I think to ask for the full name as one field that not try to change it, but use it exactly as provided for official purposes, and to also ask for a preferred name for your communication with them. In cases were you share the name to other people, e.g. an online community, you might want an additional display name which might well be different again.