Using the website I confirm that we are pointed at the correct (Bangkok) transmitter (45km). Using the little 3 element Yagi antenna recommended by MegaHome we get 100% signal and quality on all channels

Interestingly, the MiL's place in PhaChi also suggests the BKK tower (81km) rather than the closer Singburi transmitter, I wonder if the baby Yagi will work from there or we'll need something with a bit more oomph.

It's a shame the site doesn't indicate recommended antennas (or does it somewhere else?).

Usually a 4 element antenna is recommend for reception up to about 50km and a 14 element antenna up to 70km. But there are so many reception factors that can affect reception for the worst or better a person is usually better buying the largest antenna he can easily mount unless he knows a neighbor is already using a certain sized antenna with good reception results. Even a 14 element antenna goes for only around Bt350 like this one shown at this 9sats.com webpage (google translate is your friend at this web site but converts to fairly OK English) compared to a 4 or 5 element antenna running around Bt200. The 4 element antennas seem to be consistently rated for distances out to 50km although your results may vary like reaching out much further since you are just in a good reception zone.

Now have all Channels ,after moving the aerial to several positions around the roof.I got the tiny lttle Wisdom box .Anyway it has the relevant connections and reception is excellent .

Thanks for all tips and answers! Seems that more people than me alone were struggling...