It's not clear why it would be better for Frasers Hospitality (FHT SP)'s assets to be unlisted rather than listed, so this is purely financial not strategic given the ownership.
Atlas Arteria (ALX AU) boasts low risk, stable yielding, toll road assets. That's an attractive proposition for cash-up IFM, which now has a 15% economic interest.
If DTAC TB / TRUE TB's merger goes through, the top two players control ~96% of the market. Even the generally complicit Thai regulator might be reluctant to grant approval.