Parcel By Air takes around 1 month to arrive, and yes, it means long processing time at every processing center, as they consolidate shipments by routes and send them out,say, weekly. Also, events are often entered retrospectively, i.e. may be parcel had left already on Friday, and it will be entered on Monday in a sysrem.
Net time of movement by air is quite short, but usually going through few hubs with processing time in each of it.
Over the land parcels take ca.2 months to arrive - in contrast.
Most of tourists come on visa exempt entries for 15-20 days or less, or at least on VoA. Minor fraction of all tourists come for a longer period, many of them still on visa exempt entries, only part of them would require upfront , and even smaller numbers are getting all the rest of kinds of visas.
Hence, these all issues about visas at embassy and consulates have no relation at all to immigration experiences of absolutely vast majority of tourists.
those who are rejected are put in a kind of detention facility in immigration outpost, that's true if word "prison" can be synonymous to "detention" in this context
from the immigration laws of other countries and of Kingdom of Thailand, as the latter one did not follow a prevalent system of an immigration laws, found in other countries)