Laughable, risible, ludicrous, ridiculous, comic, comical, farcical, droll, funny are comparable when they mean provoking or evoking laughter or mirth.
Laughable is the general term for whatever is fit to provoke laughter.
Risible is a close synonym of laughable and in this sense, like the former, carries no special connotations.
Ludicrous applies to what induces usually scornful laughter because of its absurdity, incongruity, or preposterousness.
Ridiculous applies to what excites derision because of extreme absurdity, foolishness, or contemptibility. Comic and comical are becoming distinct in implications and in applications, although they are sometimes interchangeable.
Comic is applicable especially to something that partakes of the spirit of comedy and particularly of the literary form which aims to present life in a way that does not leave a painful impression and that does evoke smiles or laughter, especially thoughtful laughter, or amused reflection.
Comical applies not so much to the character of what induces laughter as to the impression it produces upon the observer; hence, it aptly describes something which arouses spontaneous and unrestrained laughter.
Farcical is often used interchangeably with comical but it is especially appropriate when what creates amusement is, like dramatic farce, dependent upon extravagance, nonsense, practical jokes, or burlesque for the effect it produces.
Droll and funny usually impute oddity or strangeness to what makes a thing laughable, but droll ordinarily carries a stronger implication of unfamiliarity, quaintness, absurdity, or intentional humorousness and funny of queerness or curiousness.
Funny is, however, the ordinary informal term interchangeable with any other word of the group.