Is it normal to get a double chin when looking down like this for a skinny person? (photos)

It is somewhat hard to evaluate you based on the photos you submitted. It is normal to have some fullness underneath your chin with you flex your neck. If you have some fullness underneath your chin when you are looking straight ahead, however, this is likely due to fat. Fat accumulation underneath the skin tends to be a hereditary trait that can be seen even in very thin individuals. It often does not respond to weight loss. Kybella (deoxycholic acid) injection is currently FDA approved for improvement in the appearance of convexity or fullness associated with submental (underneath the chin)  fat in adults. Kybella is injected as a solution below the skin surface into the fatty tissues. It acts by destroying fat cells in the area injected. The lysed fat cell contents create an inflammatory reaction, resulting in skin contraction and tightening (in addition to reduction of fat). Kybella treatments consist of a series of injections spaced a few months apart to improve contour in even the fattest of necks without surgery. The amount of treatments with Kybella required is directly related to the amount of fat present underneath the chin. Both liposuction and Kybella injections are equally effective in treating the fat underneath the chin. Kybella is a non-surgical option, resulting in gradual improvement. There is modest swelling after the treatment and is directly related to the amount of fat present and the amount of kybella injected. For patients who do not mind a surgery and want instant results, submental liposuction may be a better option. Submental liposuction is a 1-hour procedure with 3 small incisions (underneath the chin, and behind both ear lobes). There is minimal swelling and minimal bruising, and I do recommend wearing a compression garment for a week. In summary, both kybella and submental liposuction are both excellent option for the removal of unwanted fat underneath the chin. Kybella is ideal for patients who prefer to avoid surgery, who cannot afford a few days of down time, and are ok with results that will gradually improve over time with repeat injections. Liposuction is probably ideal for patients who are ok with a small procedure, who have a few days available to wear a compression garment, and are looking for a 1-time treatment. In order to determine if you are a candidate for any of these procedure, a proper physical exam is necessary by a facial plastic surgeon.  

Yes your chin is normal. You should not pursue any treatment. you need some slack in the chin otherwise you would not be able to tilt your head back.

Although not all a double fold when looking down, it is not that uncommon. It often relates to genetics, skin tone and also laxity of the skin. There can also be a small amount of fat under the chin that is not that noticeable when one keeps the head in an upright position. If your surgeon determines that there may be some fat, liposuction may help tighten about skin. It is also true as we get older, our skin gets looser! Even skinny guys looking down get the fold in the tummy region as you get older.