How to write down sound of laugh in speech

Question

I'm listening to some dialogues in Japanese and I write them down. I need to write down sound of laughter in sentence (speech) like in English for example

Ha ha

What I need should have notion of laughing at someone. Is it just simple

「ハハ」

Answer 1

That is fine. Alternatives are:

クスクス 'silently laughing while making fun of someone'
ウフフ 'smiling somewhat silently and often happily'
エヘヘ 'smiling because of being ashamed'
デへへ 'smiling with a slight implication of 変態-ness'
アハハ, ワハハ, ワッハッハ 'giggling'
ガハハ 'giggling out loud or a fat person giggling'
ゲラゲラ 'giggling continuously'

A famous ambiguous sentence when written in hiragana, showing the importance of having hiragana, katakana, and kanji:

ははははははとわらった。
Interpretation 1: 母はハハハと笑った。
Interpretation 2: ハハハハハハと笑った。

Answer 2

Someone pointed out to me that all of the "H" group sounds (is there a name for them?) are laughing sounds. I forgot what the nuances were, but I'll refer to this Pera Pera Penguin's 5-minute Japanese Class by Hitomi Hirayama.

はははは - normal laugh
ひひひひひ - conniving laugh
ふふふふふ - creepy laugh; feminine laugh
へへへへへ - shy laugh
ほほほほほ - [elder] feminine laughter

Prefixing an the appropriate vowel alters the meaning:

あはははは - conniving laugh
いひひひひひ - [elder] feminine laughter
うふふふふふ - creepy laugh; feminine laugh
えへへへへへ - normal laugh
おほほほほほ - embarrassed laugh; shy laugh