My bet is that someone in the decision-making process has connections with someone who supplies and/or fits these. And the more that are laid, the more kick backs are paid. It's the same near where I live, but with the super thick paint rumble strips, which are everywhere, except where they would benefit safety.
Here this road is a single lane country road behind a temple and they have managed to paint THREE sets of these rumble strips in 30m, AFTER a tight bed, to warn drivers of a bridge that has an elevation of about 45-60cm. The pic was taken before they did this.
On the flip side outside Nonthaburi Provincial court there are three of these concrete speedbumps, but ZERO warning, so you hit the first one at speed then you don't know how many more there are, if any. It's total greedy retardedness. https://maps.app.goo.gl/y57DcBTGpgXRNL7y9