All this is, on paper, an imposing organization. In practice, it cannot be said that local self-government has been a marked success. The Assemblies are far too large and unwieldy; a Commune Assembly has not less than nine members and a City Assembly thirty-six or more. The Assemblymen, untrained in debate and inexperienced in public work of this nature, are often incompetent or worse. The electorate is apathetic; usually less than five per cent trouble to record their votes. The Councillors and executive employees of the municipality are often inefficient, and not infrequent corrupt. The locally-collected revenues are quite inadequate to cover expenditure, and large loans and grants have to be made by the central Government.The act which is referenced here is most likely the Thesaban Act of 1953 (พระราชบัญญัติเทศบาล พ.ศ. ๒๔๙๖), which was not just an amendment of the 1939 Thesaban act but a whole new law. My Thai is not good enough to read 36 pages of law text, let alone find the differences between the earlier one and this one, but what I can note are the differences between the current municipal administration and the aspects mentioned above. The size of the Assemblies has been reduced either with that law or with a later amendment, as today there are between 12 (subdistrict municipalities) and 24 (city municipalities) assemblymen, compared to the 36 or more mentioned above. I only know about the hired city manager as a concept used in the special administrative area of Pattaya, the mayors of the normal municipalities were either elected by the assembly and more recently directly elected by the voters. But I have no idea if in the 1950s there were hired managers as well, or if this was only under discussion and not made it into the law.
The Government has not failed to realize this rather sorry state of affairs; though for political reasons - especially because many of the municipal councillors are also prominent politicians with a following - the Government cannot abolish local self-government altogether. An expert committee was recently set up to examine the whole system and to suggest any necessary reforms. This Committee has now made its report and has prepared a draft Act which would thoroughly reorganize the whole machinery. In particular it has been proposed to place the management of each municipality under a trained administrator (a sort of city manager as employed in cities in the United States), to inaugurate a more efficient system of regular audit of accounts, and drastically to reduce the size of Assemblies. It is believed that this draft act has been under the consideration of the Council of Ministers and has been recently been discussed in parliament.
Another thing which has changed in the last 60 years is the funding, at least with the decentralization in the 1990s the funding has much improved, and as one can see by the often very representative municipality administration buildings at least some have ample money to spend. Also the voter turnout has improved, though I don't know if this is due to an increased interest in the local administration or the fact that voting is now mandatory, nowadays the turnout is usually above 50%, at least for those cases where I have found the detailed local election results. On qualifications of the assemblymen today I cannot comment as I simply don't know well enough about it, but doubt it is same bad as 60 years ago.