Had to ask this in electronics, would like to hear this from people who have been involved. I am not a native English speaker, and I couldn't find a definitive answer online: there are too many variants that looked odd to me. There probably should be a way engineers pronounce this word?
I'm a retired US electrical engineer who spent his time in defense electronics research at a fairly well-known defense laboratory associated with MIT. I've lived all my life in New England.
I've never heard anything other than KIL-om. Short i, long o. From your point of view, as if it is "kill ohm", with the accent on "kill". The accent is not strong, and is sometimes absent. Likewise one million ohms is "MEG ohm", with the e being pronounced as if it is a long a, as is done with the words "peg" and "leg".
Informally, among other electronicers, a kilohm would simply be called a "K". As in "ten k". For larger resistances, just "meg".
EDIT. As has been mentioned in comment, the Brits apparently pronounce both o's. So you should consider tailoring your pronunciation to whichever side of the ocean you expect to talk to.
9.3 Spelling unit names with prefixes
When the name of a unit containing a prefix is spelled out, no space or hyphen is used between the prefix and unit name (see Sec. 6.2.3).
Examples: milligram but not: milli-gram kilopascal but not: kilo-pascal.
Reference  points out that there are three cases in which the final vowel of an SI prefix is commonly omitted: megohm (not megaohm), kilohm (not kiloohm), and hectare (not hectoare). In all other cases in which the unit name begins with a vowel, both the final vowel of the prefix and the vowel of the unit name are retained and both are pronounced.