Useful and more convenient than carrying a passport. However, it doesn't appear to do anything that a passport can not. I would still want to take my passport for all of the examples you have given because as this is Thailand it's very likely that ONLY a passport will he accepted however much you explain and plead as 'that's what the staff member was told/that's what the outdated form states' etc. etc.
Nice to know they exist though. If I can get one I will. Posted a Jiffy bag/padded envelope yesterday at the local post office. Was told I need my passport. Showed my Thai DL and it was accepted but I was explicitly told next time I will need my passport to post anything.
Try posting something and show your new ID, see how you get on
Sure, of course it's not meant to replace a passport per se, but as a Thai language ID card issued for a specific purpose, it does largely achieve that purpose.
I would still say, carry your passport around when you know you will need it. However, for most everyday purposes where ID is requested, this ID card can replace your passport.
For domestic air travel in Thailand (I don't really fly domestically anymore) but still, a passport is not required. A Thai DL already does the trick, but presenting the pink card is even better.
I have been showing only my Thai DL for checking into hotels here for years. Even when I've had my passport with me I don't show it (which I obviously need to carry when traveling overland to neighboring countries). Even so, when a hotel instinctively asks for my passport, they get my Thai DL and this has been questioned only once, and I travel a lot. In 2014 one hotel in Mae Sot of all places wanted to see a passport (out of the 4 people in my group) I grabbed one of my Vietnamese friend's passports and this was accepted for all guests. I can't speak for all hotels and I know some hotels/towns/cities are stricter than others but aside from that one incident where I was traveling with others anyway I have never needed it. Not in Bangkok, Phuket, Chiang Mai, Lampang, Isarn, Krabi and a host of other places. However, as I speak/read Thai fluently I seem to be able to get away with things that English only speaking expats/foreigners can't.
I can imagine a pink ID card wouldn't be rejected for hotel check-ins - besides, some migrant workers effectively use these cards in place of their passports/temporary passports. Although they typically don't travel (I think they aren't allowed to) but can't imagine a hotel clerk would demand a passport from a Burmese worker in possession of such a card.