Spaced out superscript vowels and tone marks

Why are diacritic vowels and tone-marks spaced out after the base consonants in some applications?

One reason for this is that the font Arial Unicode MS has been selected (sometimes by default) for use with Lao text. That font does not display Lao text correctly, positioning diacritic vowels and tone marks after the base character instead of above or below that character.

A less common reason is that in some older applications when superscript or subscript vowels or tone marks are typed, they can force a space to appear before the following character, due to a problem with the RichText control included with Windows. Although a modification to older Lao fonts sometimes avoided the problem, that modification is not possible with Lao Unicode fonts, and the best advice is to upgrade to a newer version of the application or use a different application for your needs.

If you are using Windows 10, simply replace the font for the affected text by DokChampa or another Unicode-coded Lao font.