New Tai Tham Characters Proposal

Some characters are still missing from Tai Tham Unicode block to cover Lao/Esaan Tham.

Double-dotted Final KA

Shape:	Two horizontal dots below base character
Similar:	U+0324 COMBINING DIAERESIS BELOW
Function:	Final KA for syllable

According to tutorials available in North-Eastern Thailand (Siswang pp. 13, Matwiset pp. 1), there are 4 possible ways to write final KA in a syllable:

Normal KA (U+1A20), when space below and above base consonant are occupied,
Subjoined KA (SAKOT + HIGH KA), when space below base consonant is available,
Mai Sat (U+1A62), when space above base consonant is available,
Double dot below base consonant, when space below base consonant is available, mostly used with short vowels.

The last one is relatively rare, but it does exist in some manuscripts, for example:

<LOW CA, VOWEL OO, DOUBLE DOT KA> (โชก)
<NA, VOWEL O, DOUBLE DOT KA> (นก)
<MA, MAI SAT, DOUBLE DOT KA> (มัก)
<NA, MAI SAT, DOUBLE DOT KA> (นัก)

Note, however, that this spelling is not found in a tutorial from Lao PDR (pp. 41-45).

Abbreviated Vowel AE

Shape:	Curve above base consonant, with ring hook on below left
Similar:	U+1A6B TAI THAM VOWEL SIGN O
Function:	Vowel AE

The word Lae (แล) can be written with abbreviate form using LA and the abbreviate vowel AE. It is sometimes merged into U+1A53 TAI THAM LETTER LAE.

Although tutorials (Matwiset pp.11, Mahasena, pp.19) only mention a few examples of the abbreviated vowel AE, there exist some other words written with this form, such as:

<HIGH KA, ABBREVIATED VOWEL AE> (แก่)
<HIGH KA, ABBREVIATED VOWEL AE, SAKOT, WA> (แก้ว)
<HIGH KA, ABBREVIATED VOWEL AE, SAKOT, WA> (แก้ว)
<LOW TA, VOWEL AE, SAKOT, LA, ABBREVIATED VOWEL AE> (แท้แล)
<LOW CA, SAKOT, LA, ABBREVIATED VOWEL AE> (ชะแล)
<HIGH HA, ABBREVIATED VOWEL AE, SAKOT, NGA> (แห่ง)

Note that in the manuscript of the first three samples (botsutkhwan.html), the abbreviated vowel AE is consistently written differently from U+1A6B VOWEL SIGN O. Abbreviated vowel AE is with ring hook, while vowel sign O without. The same is true for the tutorials (Matwiset pp.11, Mahasena, pp.19).

In bodhi.html, the two signs are quite similar, but te ring hook looks a little bit bigger for abbrevieated AE.