[RPG] Besides these creatures, what other burrowing monsters leave a tunnel behind

That sounds like an entirely legal (and evil) strategy. I like it.

The kobold wizard, buried 10 feet underground, would begin suffocating, though the chamber would plausibly have a minute's worth of air.

Since the Asabi wouldn't leave behind a tunnel, the wizard would have a great deal of difficulty in casting any spells with a somatic component. A generous GM might allow a concentration check as if grappled (ie., DC 20 + spell level) to cast such a spell. Similarly, a generous GM might allow the kobold some kind of check to avoid being buried alive (perhaps Grapple to hold on to the Asabi, perhaps Climb to scramble up in its wake).

Analysis of AD&D treasure types.

There are considerably more monsters for AD&D so here is a doc that lists out each monsters.

A is no longer the Man Treasure Type, is not commonly used either being reserved for the Lich, Locathah, Men Bandits, Squid Giant, and Troglodytes

B to F are still pretty much like their OD&D counterpart with the same rough ascending order of value.

G is no longer just for dwarves. Elves are thrown in as well as a bunch of other creatures.

H is still the hoard treasure for Dragons. Interesting the white dragons don't get this treasure type. Along with the Dragons the Archdevil Geryon and the Guardian Naga have this treasure type.

I Interestingly the Roc has been removed from I but more creatures were assigned to this treasure type than OD&D. It also was used a lot with creatures with multiple treasure types, probably because of the Gem and Jewelry values.

Now to the new types

J to N are meant to be assigned to individual monsters. When listed as part of a lair it looks to be incidental treasure. This especially clear for the various varieties of Giant Spiders.

O and P are low value coin treasure types, O is copper and silver, while P is silver and electrum

Q is a used a lot and in conjunction with other treasure types, It is the Gem treasure type.

R treasure type is similar to G but without any magic items.

S is the potion treasure type

T is the Scroll treasure type

U is a high value treasure type with Gems, Jewelry and magic items. The elite monsters that get this are Orcus, Asmodeus, Tiamat the Chromatic Dragon, and interestingly enough Ixitxachitl Guards and Androsphinxs.

V is just magic items

W is similar to G and R but with map instead of magic items. It only used for the Men, Buccaneers.

X is miscellaneous magic items plus a potion, it been assigned to a lot of monster in conjunction with other treasure types.

Y is just gold pieces

Z is similar to H with a smaller number of magic items the monsters that get this are Men Dervishes, Men Nomads, and Will-o-the-wisp. Looks like there is a lot of wealth hidden underneath those camel sacks.