Yes, I was around for some time.
At my first glance, I feel these two blades are not Siamese. Both of them are likely to be from Burma side. But as you mentioned, many elements are interchangable between ethnic groups.
The first one 's quite obvious Shan/Tai style blade. The fuller 's running to the tip 's quite rare for Siamese. Although its handle 's longer than many Burmese Dha. Shan/Tai Dha with longer hilt 's not very uncommon.
From the first glance, facetted furrule and flat/fat lotus of the second one remind me Tai origin. However, some Siamese Dahb also decorated with octagonal furrule. And the flat/fat lotus 's not very big (Tai 's Dha usually carry bigger lotus). It 's also possible to be Siamese origin. One impotant point 's in scabbard decoration. Stye of the lotus petal can be associated with LanChang people. Which was covered the north-eastern area of Thailand. So, another possibility 's Lao origin or craftmanship.