The collapse of recent sessions of the House of Representatives due to the lack of a quorum is a serious threat to the political institution -- but not one that is unprecedented in the history of Thai democracy.
Despite the fact that the prime duties of MPs are to serve as legislators, meaning they should attend their "office" (the House) to vet draft laws, it is common knowledge they often skip House sessions, or act childishly and irresponsibly by asking their friends (other MPs) to sign in on their behalf.
Such behaviour usually occurs whenever a sitting government has a decisive majority. Under such circumstances, MPs from a majority faction are emboldened by their majority votes and sometimes feel at liberty to skip any sessions they may see as being low priority.