There are no glyphs available. Your display engine (browser) indicates this by displaying the hex number of the UTF-8 character. It uses the box to indicate this behavior. Your characters have been probably encoded incorrectly.
Edit:
Corresponding to utf-8 icons the character 0x0E5C belongs to the Thai subset of UTF-8. But there is no name for that character while the previous is named KHOMUT. So you used a reserved but not used character.
Additionally you need a font that includes the glyphs for the character. Since 05EC doesn't have a name at utf-8 icons it's possible that it is not included in your font.